1. Field of the Invention
The present invention relates to machines intended for bending pipes and relates more particularly to a guide strip control device of a pipe bending machine.
2. Prior Art
In such a machine, the bending tool usually comprises: a rotary shaping roller, with a vertical axis, exhibiting on its periphery an annular groove and supporting a first jaw, a second jaw carried by a bending arm mounted to pivot around said vertical axis, the second jaw working with the first jaw to grip and carry the pipe to be bent, and a horizontal guide strip, parallel to the unbent part of the pipe, located behind the jaws and provided to be applied laterally against the pipe to be bent.
Thus, to achieve a bend in a part of the pipe, this part is gripped between the two jaws and carried forward by rotation of the bending arm, to be wound in the groove of the shaping roller. The angle of rotation of the arm determines the bending angle, and the radius of the shaping roller determines the radius of the bend formed in the pipe. The guide strip applied laterally against the pipe behind the part being bent avoids any undesired deformation of the pipe outside the part to be bent, and transmits to the machine frame the forces developed in the pipe during bending.
The guide strip can move relative to the frame, transverse to the initial direction of the pipe to be bent, to release this pipe to allow its introduction, its advance and its withdrawal. In some machines, this guide strip can, in addition, be moved longitudinally to follow the advance of the pipe during bending.
In pipe bending machines with automatic operation, the pipe to be bent is gripped in its straight part by a gripping chuck carried by a carriage that can be moved in the longitudinal direction. The carriage controls the advance of the pipe and assures, in its stop positions, the positioning of the pipe relative to the bending tool, for making the successive bends in this pipe.
When the carriage comes close to the bending tool, the guide strip, by its presence, constitutes an obstacle to the passage of the carriage, and must be retracted laterally. There is no drawback there, because the pipe is held by the grip of the carriage in its part close to the bending tool.
On the other hand, when the carriage is distant from the bending tool, the pipe has a part of considerable length which, when the guide strip is away from it, is no longer supported by this guide strip, and juts out. Then to support the straight part of the pipe, it is necessary to resort to devices. For this purpose, mobile supports are especially provided distributed over the length of the machine frame and controlled either mechanically by the advance of the carriage or by pneumatic or other means; these supports, upholding the pipe at several points, retract one after the other as the carriage advances.
Such a unit of supports, with their control means, constitutes a complicated, expensive and inefficient device; in particular, adjustment of the device is inconvenient because it requires an intervention on each of the supports.